Recombinant pseudomonas exotoxin with increased activity

Abstract

This invention relates to the production and use of recombinant Pseudomonas-derived toxins modified to increase their toxicity and potency in therapy. More particularly, the invention relates to certain deletions in domain II of the amino acid sequence of Pseudomonas exotoxin the domain which relates to the toxin's natural proteolytic processing.

What is claimed is: 
     
       1. A method for impairing tumor growth in a patient comprising administering to the patient intravenously, into a body cavity or into a lumen of an organ a ligand binding agent specific for a tumor cell, fused to a recombinant Pseudomonas exotoxin molecule in which: (a) domain Ia is deleted;   (b) from 1 to 28 amino acids from the amino terminal end of domain II are deleted;   (c) a methionine occurs at the resultant amino terminal of said molecule; and,   (d) said molecule has increased toxic activity to a target cell as compared to an unmodified PE40.   
     
     
       2. The method of claim 1, wherein the recombinant Pseudomonas exotoxin molecule has amino acids 280 to 364 and 381 to 613 of Sequence ID No: 1 wherein residue 364 is peptide bonded to residue 381. 
     
     
       3. The method of claim 1, wherein the Pseudomonas exotoxin molecule includes a substitution of serine for the amino acid cysteine at position 287 of Sequence ID No: 1. 
     
     
       4. The method of claim 1, wherein the molecule further includes an amino acid sequence at a carboxyl terminal end of the molecule selected from the group consisting of REDLK, REDL, and KDEL. 
     
     
       5. The method of claim 1, wherein amino acids 604-613 of domain III in Sequence ID No: 1 are retained in the Pseudomonas exotoxin molecule. 
     
     
       6. A method for impairing tumor growth in a patient comprising administering to the patient intravenously, into a body cavity or into a lumen of an organ a ligand binding agent specific for a tumor cell, fused to a recombinant Pseudomonas exotoxin molecule (PE) having a deletion in the amino terminal end of domain II such that the molecule is at least 20 times more cytotoxic to target cells than unmodified PE40 in a cytotoxicity assay wherein the cytotoxicity to the target cells of unmodified PE40 and the recombinant PE molecule is measured by assaying against the target cells (i) unmodified PE40 fused to a ligand binding agent specific for the target cells and (ii) the recombinant PE molecule fused to a ligand binding agent specific for the target cells.